Hey Dave, what kind of filler do you use?
Seriously, I'll have to try that, as I've used the Sherwin Williams spackling numerous times for wall repair when working with a contractor friend, but never for model filling. I was concerned about it bonding to wood, but apparently it works well. I haven't been thrilled with the brand name fillers such as Hobbico, as they tend to flash harden between layers which makes is impossible to sand an even surface, they melt when ironed over, and also do not fine sand well. Looks like you've gotten good results with the SW stuff. As things tend to go, the LHS had DHP brand for a short while, which seemed better than the Hobbico, but they never got it again.